Temperature detecting unit and fixing apparatus

ABSTRACT

A temperature detecting unit including a temperature detecting sensor, a window member, and a frame which holds the window member. The temperature detecting sensor receives infrared rays radiated by an object, thereby detecting the temperature of the object without contact with the object. The window member is arranged between the object and the temperature detecting sensor, and transmits the infrared rays. The window member includes a surface with a fluorination organic compound.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a temperature detecting unit fordetecting the temperature of an object without contacting the object anda fixing apparatus.

2. Description of Related Art

There is a conventional temperature detecting device for detecting thetemperature of the object without contacting the object. The temperaturedetecting device includes a temperature detecting sensor which receivesinfrared rays radiated by the object, which thereby detects thetemperature of the object without contact, and a window member, which isarranged between the object and the temperature detecting sensor andwhich transmits the infrared rays.

However the conventional temperature detecting device does not solve allof the problems presented during use in a fixing apparatus, an electricheating cooking device, or an air conditioner.

SUMMARY OF THE INVENTION

The present invention advantageously provides a temperature detectingunit that precisely detects the temperature of the object.

The present invention further advantageously provides a fixing apparatuswith a temperature detecting unit that precisely detects the temperatureof the object.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic front view showing a fixing apparatus in an imageforming apparatus according to the first embodiment of the presentinvention.

FIG. 2 is a schematic perspective view showing the temperature detectingdevice 1 of the related art.

FIG. 3 is a schematic sectional view showing inside the temperaturedetecting device 1 of the related art.

FIG. 4 is a schematic sectional view showing a sensor module 21 of afirst embodiment.

FIG. 5 is a schematic exploded perspective view showing the assembly ofa surrounding member 24 and the sensor module 21 of FIG. 4.

FIG. 6 is a schematic sectional view showing part of the fixingapparatus including the sensor module 21 of FIG. 4.

FIG. 7 is a schematic sectional view showing an alternativeconfiguration of the sensor module 21 of the first embodiment.

FIG. 8 is a schematic exploded perspective view showing the assembly ofa window member 37 and the surrounding member 24 in the secondembodiment.

FIG. 9 is a schematic sectional view showing inside the surroundingmember 24 in the second embodiment.

FIG. 10 is a schematic sectional view showing the part of the fixingapparatus in the second embodiment.

FIG. 11 is a schematic exploded perspective view showing the assembly ofa window member 37 and the surrounding member 24 in an alternativeconfiguration of the second embodiment.

FIG. 12 is a schematic sectional view showing inside the surroundingmember 24 in the alternative configuration of the second embodiment.

FIG. 13 is a schematic sectional view showing a sensor module 101 in thethird embodiment.

FIG. 14 is a schematic sectional view showing the part of the fixingapparatus in the third embodiment.

FIG. 15 is a view showing the relation between the number of the recordmedium threading and the stable temperature on the fixing roller 2 thatis detected by the sensor module 101 without the membrane 40 on thewindow member 47 in the third embodiment.

FIG. 16 is a view showing the relation between the number of the recordmedium threading and the stable temperature on the fixing roller 2 thatis detected by the sensor module 101 with the membrane 40 on the windowmember 47 in the third embodiment.

FIG. 17 is a schematic front view showing a fixing apparatus in an imageforming apparatus incorporating any of the embodiments described above.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

FIG. 1 is a schematic front view showing a fixing apparatus in an imageforming apparatus according to the first embodiment of the presentinvention. The fixing apparatus includes a temperature detecting device1 as a temperature detecting unit, a fixing roller 2 with a heater 3,and a pressing roller 4 as an opposite member. A nip is formed betweenthe pressing roller 4 and the fixing roller 2, and the pressing roller 4presses the fixing roller 2. The temperature detecting device 1 receivesinfrared rays radiated by the surface of the fixing roller 2 as anobject, then detects the temperature of the surface of the fixing roller2 without contacting the fixing roller 2. The controller not illustratedcontrols the heating value by the heater 3, based on the temperaturedetected by the fixing roller 2.

Accordingly, a toner image is fixed on a record medium 11 passingthrough the nip by the heat and the pressure. Further, damage to thesurface of the fixing roller by the temperature detecting device 1 isprevented, because the temperature detecting device 1 detects thetemperature of the surface of the fixing roller 2 without contacting thefixing roller 2.

FIG. 2 is a schematic perspective view showing the temperature detectingdevice 1 of the related art. The temperature detecting device 1 includesa frame 5 forming an opening, a can casing 6, a terminal 8, and abearing surface 10.

FIG. 3 is a schematic sectional view showing inside the temperaturedetecting device 1. The temperature detecting device 1 also includes awindow member 7 held by the frame 5, and a thermopile element 9. Thewindow member 7, which is arranged between the object and the thermopileelement 9, is formed by a silicon wafer. Thereby the window member 7transmits the infrared rays by the object.

According to the structure described above, the thermopile element 9receives infrared rays radiated by the object through the window member7, then outputs the electric signal according to the infrared raysreceived through the terminal 8. Thereby the thermopile element 9detects the temperature of the object as an electric signal withoutcontacting the object.

Further the temperature detecting device 1 can quickly detect thetemperature changes of the object by using the thermopile element 9. Onthe other hand, the output from the thermopile element 9 tends to changeby the temperature around the thermopile element 9 according to thefollowing expression.Vout=A*(Tb ⁴ −Ts ⁴).

Vout: the output voltage from the terminal 8.

A: the proportional constant.

Tb: the temperature of the object.

Ts: the temperature of the thermopile element 9.

Accordingly there is preferably arranged a thermistor (not illustrated)to detect the temperature in the temperature detecting device 1. Therebythe output signal from the terminal 8 is compensated by the outputsignal from the thermistor, then the exact temperature of the object isdetected.

FIG. 4 is a schematic sectional view showing a sensor module 21 of thefirst embodiment. A sensor module 21 includes the temperature detectingdevice 1, a printed circuit board 22 soldering the terminal 8, andelectric and signal wires 23. In this case, the sensor module 21 iscalled as the temperature detecting unit. The window member 7 includes aplane surface facing the object, which includes a membrane 40 offluorination organic formed by coating fluorocarbon resin or byspreading oil with the fluorine.

The OPTOOL DSX produced by DAIKIN INDUSTRIES, LTD. is preferably used asthe fluorocarbon resin, the DEMNUM Grease produced by DAIKIN INDUSTRIES,LTD. is preferably used as the oil with the fluorine. In this case, thecontact angle of water on the membrane 40 is 112 degrees, the frictioncoefficient on the membrane 40 is 0.13. The surface of the window member7 may directly include the fluorination organic compound without themembrane 40. The fluorination organic includes the chemical compoundused as a lubricant or a water-repellent agent like atetrafluoroethylene.

According to the structure described above, it is hard to stain thesurface of the window member 7 with time, or it is possible to removestain from the surface of the window member 7 easily, especially on theside facing the object. Thereby the thermopile element 9 can exactlydetect the temperature of the object.

FIG. 5 is a schematic exploded perspective view showing the assembly ofa surrounding member 24 and the sensor module 21 in the firstembodiment. A surrounding member 24 includes a opening 25 and a shelf26, whose internal dimension is almost same as the external dimensionsof the printed circuit board 22. The surrounding member 24 is formed ofa heat resistance plastic. The can casing 6 of the temperature detectingdevice 1 is fitted into the opening 25 while the printed circuit board22 abuts the shelf 26. Thereby the sensor module 21 fits the surroundingmember 24, then the thermopile element 9 is surrounded by thesurrounding member 24. In this case, the surrounding member 24 with thesensor module 21 is defined as the temperature detecting unit.

According to the structure described above, it is possible to reduce thetemperature of the thermopile element 9, because the surrounding member24 isolates the thermopile element 9 from the object thermally. Therebythe change in the output from the thermopile element 9 caused by thetemperature around the thermopile element 9 is reduced. Further thesurrounding member 24 also buffers the temperature changes in thesurrounding member 24, thereby it is prevented that the thermistor inthe temperature detecting device 1 does not compensate enough the outputsignal from the terminal 8 caused by the lower temperature response ofthe thermistor. Thereby the temperature detecting device 1 can preciselydetect the temperature of the object.

FIG. 6 is a schematic sectional view showing the part of the fixingapparatus in the first embodiment. The fixing apparatus includes apartition 30 arranged between the temperature detecting device 1 and thefixing roller 2 as the object, an angle plate 31 fixed to the partition30, and an angle plate 32 fixed to the angle plate 31 by a screw 32 a.The angle plate 32 fixes the surrounding member 24, thereby thesurrounding member 24, the partition 30, the angle plate 31, and theangle plate 32 are defined as the temperature detecting unit. Thepartition 30 includes a frame 45 forming an opening, thereby the windowmember 7 directly faces both of the fixing roller 2 and the thermopileelement 9. Further a holding member 35 and the frame 45 forms an openingso as not to make small the visual field angle θ where the thermopileelement 9 can peculiarly detect.

In the fixing apparatus, there are toner images, silicon oil to releasethe toner image, and wax included in the toner image on the fixingroller 2, then they are blown by the fan or gasified by heat to becomefloating stain when the fixing apparatus is use.

In this embodiment, an amount of the stain on the membrane 40 is lessthan in a comparative example without the membrane 40 with time. Furtherthe stain on the membrane 40 is much more easily removed by cleaningaway once with a nonwoven than in the comparative example. In addition,the membrane 40 prevents stain on the window member 7 from streakingafter cleaning away a few times with a nonwoven cloth as in thecomparative example. Thereby it is prevented that the stain remains onthe window member 7, and therefore the thermopile element 9 can moreexactly detect the temperature of the object than in the comparativeexample. Therefore it is possible to reduce the frequency of maintenancenecessary for the temperature detecting unit or the fixing apparatus.

Further the cleanliness achieved with the membrane 40 prevents thethermopile element 9 from detecting higher temperatures than real valuescaused by an initial thin membrane of stain that serves in a waycomparable to an antireflection coating. Thereby it is prevented thatthe temperature on the fixing roller 2 is controlled lower than thedesired temperature to compensate for the higher temperature that thethermopile element 9 detects.

In addition, it is prevented from that the thermopile element 9 detectsa lower temperature than a real value caused by thickening of themembrane of the stain. Thereby it is prevented that the temperature onthe fixing roller 2 is controlled higher than the desired temperature tocompensate for the lower temperature that the thermopile element 9detects. Accordingly, the present invention prevents a reduction inimage quality.

FIG. 7 is a schematic sectional view showing the sensor module 21 in analternative configuration of the first embodiment. In thisconfiguration, the window member 7 includes a lens-shaped surface facingthe object, which includes the membrane 40 with the fluorinationorganic. Thereby it is easy to condense the infrared rays to thethermopile element 9, then the thermopile element 9 can more exactlydetect the temperature of the object.

According to the first embodiment, it is hard to stain the surface ofthe window member 7 with time, and it is possible to remove stain fromthe surface of the window member 7 easily. Further it is possible toreduce the temperature and the temperature changing in the temperaturedetecting unit. Thereby the thermopile element 9 can exactly detect thetemperature of the object. Further it is possible to reduce thefrequency of maintenance necessary for the temperature detecting unit orthe fixing apparatus. In addition the invention prevents a reduction inthe quality of the image. Furthermore the invention prevents the visualfield angle 0 from being made small where the thermopile element 9 canprecisely detect temperature.

Second Embodiment

FIG. 8 is a schematic exploded perspective view showing the assembly ofa window member 37 and the surrounding member 24 in the secondembodiment.

FIG. 9 is a schematic sectional view showing inside the surroundingmember 24 in the second embodiment. A window member 37 transmits theinfrared rays from the object. The window member 37 is formed by a planesilicon wafer. The window member 37 is held by the holding member 35while fitting into a recessed seat or a level difference 36 and bondedto the surrounding member 24 by a bonding 38, thereby it is unnecessarythat the membrane 40 with the fluorination organic is arranged on thesurface of the window member 7. A thickness of the window member 37 is alittle thinner than a depth of the level difference 36. Thereby it isprevented that the stain remains on the surface of the window member 37after cleaning the surface of the window member 37. The thickness of thewindow member 37 is preferably 0.5 mm, and the infrared raystransmission efficiency is preferably 50%.

In this case, the surrounding member 24 includes the holding member 35,and the surrounding member 24 with the window member 37 is defined asthe temperature detecting unit. In addition, the holding member 35 andthe bonding 38 are formed so as to not make small the visual field anglewhere the thermopile element 9 can peculiarly detect. It is preferablyto cut off the portion of the level difference 36 where the windowmember 37 contacts. Thereby it is possible to make small the bonding 38that projects outwardly. Further there is preferably arranged aninsulator between the can casing 6 and the opening 25, when the cancasing 6 of the temperature detecting device 1 is fitted into theopening 25 as showing FIG. 5.

FIG. 10 is a schematic sectional view showing the part of the fixingapparatus in the second embodiment. In this embodiment, the surroundingmember 24 is directly fixed to the angle plate 31 by screws 31 a withoutthe angle plate 32. In this case, the surrounding member 24, thepartition 30, the angle plate 31 is defined as the temperature detectingunit. In addition, the window member 37 includes the membrane 40 withthe fluorination organic on the side facing the fixing roller 2.

Further a ventilator 43 as an airflow arising unit or an airflow unit,which arises the airflow between the fixing roller 2 and the thermopileelement 9 in a direction parallel to the surface of window member 37 asan air curtain, is arranged near the surface of the window member 37.The nozzle of the ventilator 43 is knife-edge shape, then the ventilator43 can blow the air equally. Thereby the floating stain gasified iseasily caught in a draft by the airflow, because the floating stain is amicroparticle. Therefore it is harder for stain to attach to themembrane 40, as the case may be, and therefore it is unnecessary toclean the surface of the membrane 40. The ventilator 43 may use theairflow from the cooling fan in the apparatus, and may be exchangeablewith a ventilator 430, which is arranged near the surface of thepartition 30.

FIG. 11 is a schematic exploded perspective view showing the assembly ofa window member 37 and the surrounding member 24 in an alternativeconfiguration of the second embodiment.

FIG. 12 is a schematic sectional view showing inside the surroundingmember 24 in the alternative configuration of the second embodiment.

In this modification, the window member 37 includes the lens-shapedsurface facing the object. The window member 37 may include the membrane40 with the fluorination organic as in FIG. 10. Thereby it is easy tocondense the infrared rays to the thermopile element 9 as showing A2 (A1is the visual field in case of the plane shape). Therefore thethermopile element 9 can more exactly detect the temperature of theobject, then this is preferable when the thermopile element 9 detectsthe temperature of a food cooked by an electric heating cooking device.

According to the second embodiment, the stain is prevented fromremaining on the surface of the window member 37 after cleaning thesurface of the window member 37. In addition, it is harder to stain themembrane 40, as the case may be, and thus it is unnecessary to clean thesurface of the membrane 40.

Third Embodiment

FIG. 13 is a schematic sectional view showing a sensor module 101 of athird embodiment. A sensor module 101 includes the printed circuit board22 fixing the thermopile element 9 inside there, a surrounding member 50including the holding member 35 and the level difference 36, and thewindow member 37. A reflecting mirror 44 is formed inside of thesurrounding member 50, which reflects the infrared rays. The windowmember 37 includes the membrane 40 with the fluorination organic on theside facing the object thereof, which is held by the holding member 35while fitting into the level difference 36 as in FIG. 8 and FIG. 9. Inthis case, the sensor module 101 is defined as the temperature detectingunit. The sensor module 101 forms an almost right isosceles trianglewhose hypotenuse is the reflecting mirror 44. Thereby the reflectingmirror 44 reflects the infrared rays transmitting the window member 37toward the thermopile element 9, then the thermopile element 9 receivesthe infrared rays. The surface of the reflecting mirror 44 may be formedby sphericity. The reflecting mirror 44 may be formed by a multiplelayer that reflects only the infrared rays. Further the window member 37may include the lens-shaped surface facing the object.

FIG. 14 is a schematic sectional view showing the part of the fixingapparatus in the third embodiment. In this embodiment, the printedcircuit board 22 is fixed to the angle plate 31, thereby the sensormodule 101 is fixed to the angle plate 31. In this case, the sensormodule 101, the angle plate 31 and the partition 30 are defined as thetemperature detecting unit. Further the partition 30 includes a frame 45forming an opening. The frame 45 and a supporting member 46 withelasticity presses and holds a window member 47 which is arrangedbetween the fixing roller 2 and the thermopile element 9, after thewindow member 47 slides into position between the frame 45 and thesupporting member 46. The frame 45 transmits the infrared rays and whichincludes the membrane 40 with the fluorination organic on the sidefacing the fixing roller 2 and on the side facing the thermopile element9.

In this case, the window member 37 is defined as a second window member,which is arranged between the frame 45 and the thermopile element 9, andwhich includes the surface facing the fixing roller 2 with afluorination organic compound. Further the holding member 35 is definedas a second frame which holds the second window member. Thereby themembrane 40 on the window member 47 definitely faces the fixing roller 2in case that inside and out of the window member 47 is opposite afterthe detached window member 47 is attached to the frame 45 again. Thewindow member 47 with the membrane 40 on both sides is preferably usedto detect the temperature of air in the room in the air conditioner,because it is easy to stain both sides of the window member 47 in theair conditioner. In addition, the window member 37 is prevented frombeing stained much when the window member 47 is detached from the frame45, because the membrane 40 is also on the window member 37.

Further the ventilator 43 and a suction member 48 are defined as anairflow arising unit, which provide airflow between the fixing roller 2and the thermopile element 9 in a direction parallel to the surface ofwindow member 47, and which is arranged near the surface of the windowmember 47. The ventilator 43 sends air, and the suction member 48, whichis arranged with the window member 47 between the ventilator 43 and thesuction member 48 sucks the air. Thereby the airflow in the directionparallel to the surface of window member 47 stabilizes. The suctionmember 48 may use the negative pressure caused by the cooling fan in theapparatus. Then a filter (not illustrated) may remove the stain in theair sucked by the suction member 48, and then the air is discharged tothe outside the apparatus or is received in the apparatus.

FIG. 15 is a view showing the relation between the number of the recordmedium threadings (in thousands, K) and the stable temperature on thefixing roller 2 that is detected by the sensor module 101 without themembrane 40 on the window member 47 in the third embodiment.

FIG. 16 is a view showing the relation between the number of the recordmedium threadings (in thousands, K) and the stable temperature on thefixing roller 2 that is detected by the sensor module 101 with themembrane 40 on the window member 47 in the third embodiment.

The experiment was held in the condition that there was no ventilator43, no suction member 48 and no window member 47, and that the OPTOOLDSX produced by DAIKIN INDUSTRIES, LTD formed the membrane 40 on thewindow member 37. The thickness of the membrane 40 was 1 μm, and thecontact angle of water on the membrane 40 was 105 degree, and thefriction coefficient on the membrane 40 was 0.15.

The experiment was held in the fixing apparatus of the copier in thecondition that the record medium continuously threaded, and the tonerimage forming the text pattern was fixed on the record medium asoccupying 60% area of the record medium, and the desired temperature onthe fixing roller 2 was 187° C. The 300,000th record medium threading isthe desired value at which periodical maintenance is performed in thefield.

In FIG. 15 and FIG. 16, the black triangle shows the temperaturedetected by the thermopile element 9, and the black square shows thetemperature detected by the temperature sensor contacting on the fixingroller 2 as a real temperature. In both of FIG. 15 and FIG. 16, thetemperatures detected by the thermopile element 9 stabilize near 187° C.with time, however the differences between the real temperature and thetemperature detected by the thermopile element 9 increase with timecaused by the stain on the window member 37.

The temperature difference is about 2.5° C. in FIG. 16, but thedifference temperature is about 5.5° C. in FIG. 15 after 300,000 of therecord medium threadings. In the fixing apparatus, the temperaturedifference within 2.5 □ is no problem. In other words, it is hard tostain the surface of the window member 37 with time, thus the thermopileelement 9 can exactly detect the temperature of the fixing roller 2 inFIG. 16. Further in this experiment, the stain on the membrane 40 iseasily cleaned away with alcohol. These results can be achieved usingthe DEMNUM Grease produced by DAIKIN INDUSTRIES, LTD instead of theOPTOOL DSX.

According to the third embodiment, it is hard to stain the surface ofthe window member 37 with time, and it is possible to remove stain fromthe surface of the window member 37 easily. Thereby the thermopileelement 9 can exactly detect the temperature of the fixing roller 2.Further it is possible to reduce the frequency of performing maintenanceon the temperature detecting unit or the fixing apparatus.

Regarding All Embodiments Described Above

FIG. 17 is a schematic front view showing a fixing apparatus in an imageforming apparatus for use with all embodiments described above. Thefixing roller 2 and a tension roller 19 support a fixing belt 20 as afixing member and the object, the thermopile element 9 detects thetemperature on the surface of the fixing belt 20. The thermopile element9 may be arranged below the fixing member and upstream near the nip asshown by the dotted lines. Thereby the thermopile element 9 can exactlydetect the temperature on the fixing belt 20 without the influence ofthe convective heat.

Further the object may be a food cooked by an electric heating cookingdevice or air in a room whose temperature is regulated by an airconditioner instead of the fixing member.

The present application claims foreign priority to 2002-205840, which isincorporated by reference herein in its entirety.

1. A fixing apparatus, comprising: a fixing member which heats a tonerimage; an opposite member which forms a nip between said fixing memberand said opposite member, where said toner image is fixed on a recordmedium passing through said nip; a temperature detecting sensor whichreceives infrared rays radiated by said fixing member, thereby detectingthe temperature of said object without contact with said object; awindow member, which is arranged between said fixing member and saidtemperature detecting sensor, and which transmits the infrared rays; anda frame which holds said window member, wherein said window memberincludes a surface with a fluorination organic compound.